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Showing papers by "University of California, San Francisco published in 1993"


Journal ArticleDOI
02 Dec 1993-Nature
TL;DR: Finding that mutations in the gene daf-2 can cause fertile, active, adult Caenorhabditis elegans hermaphrodites to live more than twice as long as wild type raises the possibility that the longevity of the dauer is not simply a consequence of its arrested growth, but instead results from a regulated lifespan extension mechanism that can be uncoupled from other aspects of dauer formation.
Abstract: We have found that mutations in the gene daf-2 can cause fertile, active, adult Caenorhabditis elegans hermaphrodites to live more than twice as long as wild type. This lifespan extension, the largest yet reported in any organism, requires the activity of a second gene, daf-16. Both genes also regulate formation of the dauer larva, a developmentally arrested larval form that is induced by crowding and starvation and is very long-lived. Our findings raise the possibility that the longevity of the dauer is not simply a consequence of its arrested growth, but instead results from a regulated lifespan extension mechanism that can be uncoupled from other aspects of dauer formation. daf-2 and daf-16 provide entry points into understanding how lifespan can be extended.

3,146 citations


Journal ArticleDOI
TL;DR: It is argued that the conversion of alpha-helices into beta-sheets underlies the formation of PrPSc, and it is likely that this conformational transition is a fundamental event in the propagation of prions.
Abstract: Prions are composed largely, if not entirely, of prion protein (PrPSc in the case of scrapie). Although the formation of PrPSc from the cellular prion protein (PrPC) is a post-translational process, no candidate chemical modification was identified, suggesting that a conformational change features in PrPSc synthesis. To assess this possibility, we purified both PrPC and PrPSc by using nondenaturing procedures and determined the secondary structure of each. Fourier-transform infrared (FTIR) spectroscopy demonstrated that PrPC has a high alpha-helix content (42%) and no beta-sheet (3%), findings that were confirmed by circular dichroism measurements. In contrast, the beta-sheet content of PrPSc was 43% and the alpha-helix 30% as measured by FTIR. As determined in earlier studies, N-terminally truncated PrPSc derived by limited proteolysis, designated PrP 27-30, has an even higher beta-sheet content (54%) and a lower alpha-helix content (21%). Neither PrPC nor PrPSc formed aggregates detectable by electron microscopy, while PrP 27-30 polymerized into rod-shaped amyloids. While the foregoing findings argue that the conversion of alpha-helices into beta-sheets underlies the formation of PrPSc, we cannot eliminate the possibility that an undetected chemical modification of a small fraction of PrPSc initiates this process. Since PrPSc seems to be the only component of the "infectious" prion particle, it is likely that this conformational transition is a fundamental event in the propagation of prions.

2,230 citations


Journal ArticleDOI
TL;DR: In this article, the femoral neck bone density was measured by dual X-ray absorptiometry is a better predictor of hip fracture than measurements of other bones, including the radius or calcaneus.

2,228 citations


Journal Article
TL;DR: Assay of microvessel density within invasive tumors may prove valuable in selecting patients for aggressive adjuvant therapies in early prostate carcinoma, and was present predominantly in the poorly differentiated tumors.
Abstract: Tumor growth and metastasis require angiogenesis; and microvessel density, a measure of tumor angiogenesis, correlates with metastasis in breast and lung carcinoma To determine how microvessel density correlated with metastasis in prostate carcinoma, we counted microvessels within the initial invasive carcinomas of 74 patients (29 with metastasis, 45 without) Microvessels were highlighted by immunostaining endothelial cells for factor VIII-related antigen Without knowledge of the patient's cancer stage, microvessels were counted in a 200 field (0739 mm2) in the most active areas of neovascularization The mean microvessel count in tumors from patients with metastases was 768 microvessels per 200 field (median, 66; standard deviation, 446) The counts within carcinomas from patients without metastasis were significantly lower, 392 (median, 36; standard deviation, 186) (P < 00001) Microvessel counts increased with increasing Gleason's score (P < 00001), but this increase was present predominantly in the poorly differentiated tumors Although Gleason's score also correlated with metastasis (P = 001), multivariate analysis showed that Gleason's score added no additional information to that provided by microvessel count alone Assay of microvessel density within invasive tumors may prove valuable in selecting patients for aggressive adjuvant therapies in early prostate carcinoma

1,737 citations


Journal ArticleDOI
TL;DR: Advances in the isolation and characterization of liver cells, in conjunction with progress in matrix and cytokine biology, have led to important new insights about the cellular basis of hepatic fibrosis, including the hepatic lipocyte.
Abstract: Hepatic fibrosis is a common response to chronic liver injury from many causes, including alcohol, persistent viral and helminthic infections, and hereditary metal overload. Emerging evidence suggests that cellular mechanisms of hepatic fibrosis are shared among these different insults and, moreover, that the liver's response is a paradigm for parenchymal wound healing in other tissues. Advances in the isolation and characterization of liver cells, in conjunction with progress in matrix and cytokine biology, have led to important new insights about the cellular basis of hepatic fibrosis. In particular, the hepatic lipocyte (also known as the stellate, fat-storing, perisinusoidal, or Ito . . .

1,456 citations


Journal ArticleDOI
TL;DR: Differences in the two isoforms in complexing with the beta/A4 peptide may be involved in the pathogenesis of the intra- and extracellular lesions of Alzheimer disease.
Abstract: Apolipoprotein E (apoE), a plasma apolipoprotein that plays a central role in lipoprotein metabolism, is localized in the senile plaques, congophilic angiopathy, and neurofibrillary tangles of Alzheimer disease. Late-onset familial and sporadic Alzheimer disease patients have an increased frequency of one of the three common apoE alleles, epsilon 4, suggesting apoE4 is associated with increased susceptibility to disease. To follow up on this suggestion, we compared the binding of synthetic amyloid beta (beta/A4) peptide to purified apoE4 and apoE3, the most common isoform. Both isoforms bound synthetic beta/A4 peptide, the primary constituent of the plaque and angiopathy, forming a complex that resisted dissociation by boiling in SDS. Oxygen-mediated complex formation was implicated because binding was increased in oxygenated buffer, reduced in nitrogen-purged buffer, and prevented by reduction with dithiothreitol or 2-mercaptoethanol. Binding of beta/A4 peptide was saturable at 10(-4) M peptide and required residues 12-28. Examination of apoE fragments revealed that residues 244-272 are critical for complex formation. Both oxidized apoE4 and apoE3 bound beta/A4 peptide; however, binding to apoE4 was observed in minutes, whereas binding to apoE3 required hours. In addition, apoE4 did not bind beta/A4 peptide at pH < 6.6, whereas apoE3 bound beta/A4 peptide from pH 7.6 to 4.6. Together these results indicate differences in the two isoforms in complexing with the beta/A4 peptide. Binding of beta/A4 peptide by oxidized apoE may determine the sequestration or targeting of either apoE or beta/A4 peptide, and isoform-specific differences in apoE binding or oxidation may be involved in the pathogenesis of the intra- and extracellular lesions of Alzheimer disease.

1,364 citations


Journal ArticleDOI
TL;DR: A candidate gene (Mc1) for Menkes disease is isolated and qualitative or quantitative abnormalities in the mRNA in sixteen of twenty–one Menkes patients are found and predicted to be a P–type cation–transporting ATPase.
Abstract: Menkes disease is an X-linked disorder of copper transport characterized by progressive neurological degeneration and death in early childhood. We have isolated a candidate gene (Mc1) for Menkes disease and find qualitative or quantitative abnormalities in the mRNA in sixteen of twenty-one Menkes patients. Four patients lacking Mc1RNA showed rearrangements of the Menkes gene. The gene codes for a 1,500 amino acid protein, predicted to be a P-type cation-transporting ATPase. The gene product is most similar to a bacterial copper-transporting ATPase and additionally contains six putative metal-binding motifs at the N-terminus. The gene is transcribed in all cell types tested except liver, consistent with the expression of the Menkes defect.

1,316 citations


Journal ArticleDOI
TL;DR: It is demonstrated that attended natural stimulation can modify the tonotopic organization of Al in the adult primate, and that this alteration is correlated with changes in perceptual acuity.
Abstract: Previous studies have shown that the tonotopic organization of primary auditory cortex is altered subsequent to restricted cochlear lesions (Robertson and Irvine, 1989) and that the topographic reorganization of the primary somatosensory cortex is correlated with changes in the perceptual acuity of the animal (Recanzone et al., 1992a-d). Here we report an increase in the cortical area of representation of a restricted frequency range in primary auditory cortex of adult owl monkeys that is correlated with the animal's performance at a frequency discrimination task. Monkeys trained for several weeks to discriminate small differences in the frequency of sequentially presented tonal stimuli revealed a progressive improvement in performance with training. At the end of the training period, the tonotopic organization of Al was defined by recording multiple-unit responses at 70-258 cortical locations. These responses were compared to those derived from three normal monkeys and from two monkeys that received the same auditory stimuli but that were engaged in a tactile discrimination task. The cortical representation, the sharpness of tuning, and the latency of the response were greater for the behaviorally relevant frequencies of trained monkeys when compared to the same frequencies of control monkeys. The cortical area of representation was the only studied parameter that was correlated with behavioral performance. These results demonstrate that attended natural stimulation can modify the tonotopic organization of Al in the adult primate, and that this alteration is correlated with changes in perceptual acuity.

1,276 citations


Journal ArticleDOI
10 Dec 1993-Science
TL;DR: Results suggest that APC is involved in cell adhesion, and an antibody specific to beta-catenin also recognized the 95-kilodalton protein in the immunoprecipitates.
Abstract: Mutations in the human APC gene are linked to familial adenomatous polyposis and to the progression of sporadic colorectal and gastric tumors. To gain insight into APC function, APC-associated proteins were identified by immunoprecipitation experiments. Antibodies to APC precipitated a 95-kilodalton protein that was purified and identified by sequencing as beta-catenin, a protein that binds to the cell adhesion molecule E-cadherin. An antibody specific to beta-catenin also recognized the 95-kilodalton protein in the immunoprecipitates. These results suggest that APC is involved in cell adhesion.

1,274 citations


Book ChapterDOI
TL;DR: The characterization of structural and functional diversity within the F GF receptor shows the differences in the mechanisms of action among members of the FGF family.
Abstract: Publisher Summary The fibroblast growth factors (FGFs) constitute a family of closely related polypeptide mitogens There are seven members of this family, identified on the basis of amino acid sequence homologies The FGF family has distinguished itself from other growth factor families by virtue of the pleiotropic actions of its members This chapter discusses the structural and functional diversity in the FGF receptor multigene family The effects of FGFs are known to be mediated by high-affinity receptor tyrosine kinases The structurally diverse receptor molecules are also functionally different The characterization of structural and functional diversity within the FGF receptor shows the differences in the mechanisms of action among members of the FGF family The first members of the FGF family to be purified and characterized were acidic FGF (aFGF) and basic FGF (bFGF), which are purified on the basis of their mitogenicity toward fibroblasts by using bovine pituitary Functional differences among the different receptor forms are observed in the chapter at two levels The long-range goal of designing the effective agonist and antagonists of FGF action has considerable therapeutic value

1,267 citations


Journal ArticleDOI
TL;DR: It is shown, using luciferase and beta-galactosidase containing plasmids, that dendrimers mediate high efficiency transfection of a variety of suspension and adherent cultured mammalian cells.

Journal ArticleDOI
18 Jun 1993-Cell
TL;DR: IRE1 encodes a transmembrane serine/threonine kinase that it is proposed transmits the unfolded protein signal across the ER or inner nuclear membrane, suggesting that the induction of ER resident proteins is coupled to the biogenesis of new ER membrane.

Journal ArticleDOI
26 Mar 1993-Science
TL;DR: Transfection studies indicate that the I kappa B alpha gene is specifically induced by the 65-kilodalton transactivating subunit of NF-kappa B, and association of the newly synthesized I k Kappa B alpha with p65 restores intracellular inhibition of NF -kappaB DNA binding activity and prolongs the survival of this labile inhibitor.
Abstract: The eukaryotic transcription factor nuclear factor-kappa B (NF-kappa B) participates in many parts of the genetic program mediating T lymphocyte activation and growth. Nuclear expression of NF-kappa B occurs after its induced dissociation from its cytoplasmic inhibitor I kappa B alpha. Phorbol ester and tumor necrosis factor-alpha induction of nuclear NF-kappa B is associated with both the degradation of performed I kappa B alpha and the activation of I kappa B alpha gene expression. Transfection studies indicate that the I kappa B alpha gene is specifically induced by the 65-kilodalton transactivating subunit of NF-kappa B. Association of the newly synthesized I kappa B alpha with p65 restores intracellular inhibition of NF-kappa B DNA binding activity and prolongs the survival of this labile inhibitor. Together, these results show that NF-kappa B controls the expression of I kappa B alpha by means of an inducible autoregulatory pathway.

Journal ArticleDOI
13 Aug 1993-Cell
TL;DR: Through laser ablation, chemosensory neurons that detect volatile odorants are identified and it is shown that the nematode C. elegans might have senses that correspond to smell and taste, respectively.


Journal ArticleDOI
23 Jun 1993-JAMA
TL;DR: Health insurance coverage alone is not likely to reduce significantly SES differences in health, and attention should be paid both in policy decisions and in clinical practice to other SES-related factors that may influence patterns of health and disease.
Abstract: Objective. —Socioeconomic status (SES) is strongly associated with risk of disease and mortality. Universal health insurance is being debated as one remedy for such health inequalities. This article considers mechanisms through which SES affects health and argues that a broader and more comprehensive approach is needed. Data Sources. —Published articles surveyed using MEDLINE and review articles and bibliographies. Methods and Results. —Research is reviewed on the association of SES with health outcomes in different countries, including those with universal health coverage. Socioeconomic status relates to health at all levels of the SES hierarchy, and access to care accounts for little of this association. Other mechanisms are suggested and implications for policy and clinical practice are discussed. Conclusion. —Health insurance coverage alone is not likely to reduce significantly SES differences in health. Attention should be paid both in policy decisions and in clinical practice to other SES-related factors that may influence patterns of health and disease. (JAMA. 1993;269:3140-3145)


Journal ArticleDOI
11 Mar 1993-Nature
TL;DR: The IRK1 channel and an ATP-regulated K+ channel show extensive sequence similarity and constitute a new superfamily, similar to the inner core structure of voltage-gated K+ channels.
Abstract: A complementary DNA encoding an inward rectifier K+ channel (IRK1) was isolated from a mouse macrophage cell line by expression cloning. This channel conducts inward K+ current below the K+ equilibrium potential but passes little outward K+ current. The IRK1 channel contains only two putative transmembrane segments per subunit and corresponds to the inner core structure of voltage-gated K+ channels. The IRK1 channel and an ATP-regulated K+ channel show extensive sequence similarity and constitute a new superfamily.

Journal ArticleDOI
23 Apr 1993-Cell
TL;DR: It is shown that a minor subpopulation of est1- survivors arise as a result of the amplification and acquisition of subtelomeric elements (and their deletion derivatives) by a large number of telomeres, indicating that even when the primary pathway for telomere replication is defective, an alternative backup pathway can restore telomerre function and keep the cell alive.

Journal ArticleDOI
17 Jun 1993-Nature
TL;DR: The crystal structures of the human CDK2 apoenzyme and its Mg2+ATP complex have been determined to 2.4Å resolution and the structure is bi-lobate, like that of the cyclic AMP-dependent protein kinase, but contains a unique helix—loop segment that interferes with ATP and protein substrate binding.
Abstract: Cyclin-dependent kinase 2 (CDK2) is a member of a highly conserved family of protein klnases that regulate the eukaryotic cell cycle. The crystal structures of the human CDK2 apoenzyme and its Mg2+ATP complex have been determined to 2.4A resolution. The structure is bi-lobate, like that of the cyclic AMP-dependent protein kinase, but contains a unique helix—loop segment that interferes with ATP and protein substrate binding and probably plays a key part in the regulation of all cyclin-dependent kinases.

Journal ArticleDOI
TL;DR: Recent work in the hippocampus indicates that NMDA receptor activation does not necessarily lead to induction of long-term potentiation but instead may elicit a repertoire of distinct forms of synaptic plasticity that confer increased flexibility to neural circuits involved in information processing and storage.

Journal ArticleDOI
09 Jul 1993-Science
TL;DR: A single intravenous injection of expression plasmid:cationic liposome complexes into adult mice efficiently transfected virtually all tissues and most of the extravascular parenchymal cells expressed the transgene without any apparent treatment-related toxicity.
Abstract: Direct gene transfer into adult animals resulting in generalized or tissue-specific expression would facilitate rapid analysis of transgene effects and allow precise in vivo manipulation of biologic processes at the molecular level. A single intravenous injection of expression plasmid:cationic liposome complexes into adult mice efficiently transfected virtually all tissues. In addition to vascular endothelial cells, most of the extravascular parenchymal cells present in many tissues including the lung, spleen, lymph nodes, and bone marrow expressed the transgene without any apparent treatment-related toxicity. The transgene was still expressed in large numbers of cells in multiple tissues for at least 9 weeks after a single injection. Expression could be targeted to specific tissues and cell types, depending on the promoter element used.

Journal ArticleDOI
01 Jan 1993-Cell
TL;DR: This review describes the cytological and molecular architecture of the neuromuscular junction, making three main points: that chemical synapses are designed for rapid, focal transmission of information; that this task is performed by highly specialized preand postsynaptic domains that lie in precise juxtaposition across the synaptic cleft; and that many of the components forming these domains have now been isolated and characterized.

Journal ArticleDOI
TL;DR: It is demonstrated by in situ hybridization that Flk-1 protein expression in the mouse embryo is restricted to the vascular endothelium and the umbilical cord stroma and may play a role in vascular development and regulation of vascular permeability.
Abstract: Vascular endothelial growth factor (VEGF), also known as vascular permeability factor, induces endothelial proliferation in vitro and vascular permeability in vivo. The human transmembrane c-fms-like tyrosine kinase Flt-1 has recently been identified as a VEGF receptor. Flt-1 kinase has seven immunoglobulin-like extracellular domains and a kinase insert sequence, features shared by two other human gene-encoded proteins, kinase insert domain-containing receptor (KDR) and FLT-4. In this study we show that the mouse homologue of KDR, Flk-1, is a second functional VEGF receptor. Flk-1 binds VEGF with high affinity, undergoes autophosphorylation, and mediates VEGF-dependent Ca2+ efflux in Xenopus oocytes injected with Flk-1 mRNA. We also demonstrate by in situ hybridization that Flk-1 protein expression in the mouse embryo is restricted to the vascular endothelium and the umbilical cord stroma. VEGF and its receptors Flk-1/KDR and Flt-1 may play a role in vascular development and regulation of vascular permeability.

Journal ArticleDOI
TL;DR: The observations indicate the major challenge of preventing infection by HIV appears to involve infection with a relatively low-virulence strain that remains sensitive to the immune response, particularly to control by CD8+ cell antiviral activity.

Journal ArticleDOI
16 Dec 1993-Nature
TL;DR: It is found that CDK2/cyclin complexes in mouse fibroblasts associate tightly with a 20K protein (CAP20), which represents a new negative regulatory subunit that inhibits the activity of CDK 2/cycl in mammalian cells.
Abstract: THE major events of the cell division cycle are triggered by periodic changes in the activity of cyclin-dependent protein kinases (CDKs). In mammals, the members of the CDK family include CDK2 and CDC2, which are thought to be involved in the control of DNA replication and mitosis, respectively1–3. The protein kinase activity of these enzymes is controlled by a complex array of mechanisms4–6. Activation of the CDK catalytic subunit requires association with a positive regulatory subunit (cyclin) and phosphorylation (at Thr 160 in CDK2). This activated complex can be inhibited by additional phosphorylation at Thr 14 and Tyr 15. Here we report the identification of a new mechanism for the regulation of CDK2 activity. We find that CDK2/cyclin complexes in mouse fibroblasts associate tightly with a 20K protein (CAP20). Complexes containing CAP20 were isolated from cell lysates and found to have negligible kinase activity, indicating that CAP20 association in vivo may inhibit CDK2 activity. We purified CAP20 from 3T3 cells and found that low concentrations of the protein completely inhibit the kinase activity of CDK2 in vitro. Thus CAP20 represents a new negative regulatory subunit that inhibits the activity of CDK2/cyclin complexes in mammalian cells.

Journal ArticleDOI
TL;DR: Evidence is presented to support a model based on the possibility of recombination between homologous sequences located in intron 22 and upstream of the factor VIII gene that leads to an inversion of all intervening DNA and a disruption of the gene.
Abstract: Mutations in the factor VIII gene have been discovered for barely more than half of the examined cases of severe haemophilia A. To account for the unidentified mutations, we propose a model based on the possibility of recombination between homologous sequences located in intron 22 and upstream of the factor VIII gene. Such a recombination would lead to an inversion of all intervening DNA and a disruption of the gene. We present evidence to support this model and describe a Southern blot assay that detects the inversion. These findings should be valuable for genetic prediction of haemophilia A in approximately 45% of families with severe disease.

Journal ArticleDOI
TL;DR: The hypothesis proposed in this review is that normal diurnal rhythms in the hypothalamic-pituitary-adrenal (HPA) axis are highly regulated by activity in medial hypothalamic nuclei to effect an interaction between corticosteroids and insulin such that optimal metabolism results in response to changes in the fed or fasted state of the animal.

Journal ArticleDOI
TL;DR: A neuromeric model of the forebrain is described that is consistent with the expression patterns of these genes, and that provides a framework for understanding the morphological relationships within this complex structure.

Journal ArticleDOI
20 Aug 1993-Science
TL;DR: Findings indicate that the synaptic activation of protein phosphatases plays an important role in the regulation of synaptic transmission and suggests that phosphatase activity is required for the maintenance of LTD.
Abstract: The effectiveness of long-term potentiation (LTP) as a mechanism for information storage would be severely limited if processes that decrease synaptic strength did not also exist. In area CA1 of the rat hippocampus, prolonged periods of low-frequency afferent stimulation elicit a long-term depression (LTD) that is specific to the stimulated input. The induction of LTD was blocked by the extracellular application of okadaic acid or calyculin A, two inhibitors of protein phosphatases 1 and 2A. The loading of CA1 cells with microcystin LR, a membrane-impermeable protein phosphatase inhibitor, or calmodulin antagonists also blocked or attenuated LTD. The application of calyculin A after the induction of LTD reversed the synaptic depression, suggesting that phosphatase activity is required for the maintenance of LTD. These findings indicate that the synaptic activation of protein phosphatases plays an important role in the regulation of synaptic transmission.